MD80 FLT CREW HAS FAILURE OF THEIR PRIMARY FLT DISPLAY (PFD) AND NAV DISPLAY (ND); DECLARES AN EMER AND RETURNS TO BOS WITH NO GYROSCOPE VECTORS.

Narrative

DEPARTED BOSTON FOR DFW. ALL INDICATIONS WERE NORMAL PRIOR TO TKOF. ON DEP IN THE TURN TO HEADING 140 DEGS; THE COMMAND BARS WENT OUT OF VIEW. CONTINUING THE DEP TO THE W; THE HEADINGS BECAME MISALIGNED. CONTINUING THE CLB WITH ASSISTANCE FROM CTR; WE REALIZED THAT THE PROB WAS NOT CORRECTABLE. THIS IS WHEN WE DECLARED AN EMER AND REQUESTED TO RETURN TO BOSTON. AT THIS POINT; BOTH EFIS ATTITUDE DISPLAYS AND COMPASS DISPLAYS DISAPPEARED WITH ALL OF THE ASSOCIATED FAULT SIGNALS. NOW WE WERE DOWN TO JUST THE STANDBY ATTITUDE INDICATOR; AIRSPD AND ALTIMETER. WE WERE GIVEN TURNS FROM CTR TO RETURN TO BOSTON AND DSNDED TO BELOW THE CLOUD LAYER FOR A VFR APCH AND LNDG ON RWY 22L. THIS WAS AN OVERWT LNDG AT 135000 LBS ALSO; ON SHORT FINAL; THE L WING WAS STRUCK BY A SEAGULL. MAINT MET THE ACFT AND COULD NOT SOLVE THE PROB FROM THE COCKPIT. ONCE AN INSPECTION FROM THE E&E COMPARTMENT WAS MADE; THE SYS RETURNED TO NORMAL. THE MAINT CREW COULD FIND NOTHING NOTEWORTHY WRONG WITH THE ACFT. THE SYS WERE BROUGHT BACK TO NORMAL. ALL INSPECTIONS WERE COMPLETED AND WE THEN TOOK THE ACFT TO DFW FOR AN UNEVENTFUL FLT. SUPPLEMENTAL INFO FROM ACN 583746: ONCE WE ENTERED IMC AND AT ABOUT FL250 OUR NAV DISPLAY AND ATTITUDE DISPLAY WENT BLANK. WE RECEIVED NO GYROSCOPE VECTORS BACK TO BOS AND INTO VMC.